The present invention generally relates to a method of making copolymers of vinyl monomers. More specifically, the present invention is directed to a method of making copolymers containing isobutylene type monomers.
It is often observed that monomers that do not readily homopolymerize are able to undergo rapid copolymerization reactions with each other. The most typical situation occurs when a strong electron donating monomer is mixed with a strong electron accepting monomer from which a regular alternating copolymer results after free radical initiation. Maleic anhydride is a widely used example of a strong electron accepting monomer. Styrene and vinyl ethers are typical examples of electron donating monomer. Systems, such as maleic anhydridexe2x80x94styrene, are known to form charge transfer complexes, which tends to place the monomers in alternating sequence prior to initiation. The application of the free radical initiator xe2x80x9ctiesxe2x80x9d the ordered monomers together to form an alternating copolymer (Cowie, Alternating Copolymers, Plenum, N.Y. (1985)).
U.S. Pat. No. 2,378,629 to Hanford and U.S. Pat. No. 4,151,336 to Sackmann et al. disclose that even when a moderately electron donating monomer, such as diisobutylene, is copolymerized with a strong electron acceptor monomer, such as maleic anhydride, an alternating copolymer results.
When a moderately electron donating monomer, such as isobutylene, is copolymerized with a moderately electron accepting monomer, such as an acrylic ester, poor incorporation of the electron donating monomer results. For example, free radical copolymerization of isobutylene (IB) and acrylic monomers has resulted in copolymers that contain at most 20-30% of IB and have low molecular weights because of degradative chain transfer of IB. Examples of such copolymerizations of IB are disclosed by U.S. Pat. No. 2,411,599 to Sparks et al. and U.S. Pat. No. 2,531,196 to Brubaker et al.
The ability to make copolymers of acrylic monomers and IB type monomers is desired in the art. For example, many patents express the potential for using IB-containing polymers in coating compositions. For example, U.S. Pat. No. 6,114,489 to Vicari et al. discloses a coating composition that includes a functional acrylic resin binder; a co-reactant capable of reacting with the functionality of the acrylic binder; a degasser; and a hyperbranched polyester flow and leveling agent. IB is suggested as a potential co-monomer for use in the acrylic binder as part of a long list of monomers. U.S. Pat. No. 5,552,487 to Clark et al. discloses powder coating compositions that include a copolymer having a reactive functionality and a suitable crosslinking agent capable of reaction with the reactive functionality of the copolymer. The copolymer is a made by copolymerizing functional monomers with other monomers, isobutylene being one among many listed as potential co-monomers. Although only two are referenced herein, of the many patents that express the possibility of using isobutylene-type co-monomers, none actually shows or discloses a working example of such a copolymer.
The fact that few examples of isobutylene-type monomer-containing copolymers are found is due to the generally non-reactive nature of isobutylene with acrylic and methacrylic monomers. Reactivity ratios for monomers can be calculated using the Alfreyxe2x80x94Price Q-e values (Robert Z. Greenley, Polymer Handbook, Fourth Edition, Brandrup, Immergut and Gulke, editors, Wiley and Sons, New York, N.Y., pp. 309-319 (1999)). The calculations may be carried out using the formulas I and II:
r1=(Q1/Q2)exp{xe2x88x92e1(e1xe2x88x92e2)}xe2x80x83xe2x80x83I 
r2=(Q2/Q1)exp{xe2x88x92e2(e2xe2x88x92e1)}xe2x80x83xe2x80x83II 
where r1 and r2 are the respective reactivity ratios of monomers 1 and 2, and Q1 and Q2 and e1 and e2 are the respective reactivity and polarity values for the respective monomers (Odian, Principals of Polymerization, 3rd Ed., Wiley-Interscience, New York, N.Y., Chapter 6, pp. 452-467 and 489-491 (1991)). Table 1 shows the calculated reactivity ratios of selected monomers with isobutylene:
As one skilled in the art of polymer chemistry can appreciate, when r1 is near zero and r2 has a value of 10 or more, monomer 2 is reactive toward both monomers and monomer 1 is reactive toward neither monomer. In other words, it is extremely difficult to prepare copolymers having significant amounts of both monomers. It is not surprising then that few examples can be found of coating compositions that include isobutylene-type monomer-containing copolymers, because the monomers do not tend to copolymerize.
A few examples of acrylic ester or acrylonitrile copolymers made by copolymerizing with monomers such as propylene, isobutylene, and styrene, have been accomplished in the presence of Lewis acids, such as alkylaluminum halides, to give 1:1 alternating copolymers. The alternating copolymers were obtained when the concentration ratio of the Lewis acids to the acrylic esters was 0.9 and the concentration of IB was greater than the concentration of the acrylic esters (Hirooka et al., J. Polym. Sci. Polym. Chem., 11, 1281 (1973)). The metal halides vary the reactivity of the monomers by complexing with them. The electron donor monomerxe2x80x94electron acceptor monomerxe2x80x94metal halide complex leads to alternating copolymers (Mashita et al., Polymer, Vol. 36, No. 15, pp. 2973-2982, (1995)).
Copolymers of IB and methyl acrylate (MA) have also been obtained by using ethyl aluminum sesquichloride and 2-methyl pentanoyl peroxide as an initiating system. The resulting copolymer had an alternating structure, with either low (Kuntz et al., J. Polym. Sci. Polym. Chem., 16, 1747 (1978)) or high isotacticity in the presence of EtAlCl2 (10 molar % relative to MA). (Florjanczyk et al., Makromol. Chem., 183, 1081 (1982)).
Another method for making IB copolymers with acrylic esters involved alkyl boron halide, which was found to be much more active than alkyl aluminum halides in forming alternating copolymers. The resulting copolymer was an elastomer of high tensile strength and high thermal decomposition temperature with good oil resistance, especially at elevated temperatures (Mashita et al., Polymer, 36, 2983 (1995)).
U.S. Pat. No. 5,807,937 to Matyjaszewski et al. discloses a method of making alternating copolymers of isobutylene and methyl acrylate using atom transfer radical polymerization (ATRP) processes. The method requires the use of a suitable ATRP initiator, such as 1-phenylethyl bromide, and suitable transition metal salts, such as CuBr, with a ligand, such as 2,2xe2x80x2-bipyridyl, to perform the complex redox initiation and propagation steps of the polymerization process.
Copolymers containing relatively high amounts (xe2x89xa730 mol %) of IB and acrylic esters have only been attained by free radical polymerization when Lewis acids or ATRP initiation systems have been employed. The polymer that results from such processes requires expensive and time consuming clean-up to remove the transition metal salt and/or Lewis acid residues in order to make the polymer commercially useful.
Copolymer compositions that contain Lewis acids and/or transition metals intermingled with the copolymer can have a number of drawbacks when used commercially. First, some Lewis acids and transition metals are toxic and have adverse environmental effects if they are leached from the copolymer and enter the environment. In coating applications, the Lewis acids and transition metals may lead to poor stability when exposed to UV light or simply cause the coating to discolor. In other applications, the Lewis acids and transition metals may react with other ingredients in a formulation resulting in undesired properties.
Therefore, there is a clear and present need for a method for making copolymers containing isobutylene type monomers that does not rely on Lewis acids and transition metals to obtain an alternating copolymer.
The present invention is directed to a method of making a copolymer composition containing a copolymer having alternating donor-acceptor segments. The copolymerization method includes the steps of:
(a) providing a donor monomer composition that includes one or more monomers having structure (I): 
where R1 is linear or branched C1 to C4 alkyl and R2 is selected from the group consisting of methyl, linear, cyclic or branched C1 to C20 alkyl, alkenyl, aryl, alkaryl and aralkyl;
(b) mixing the donor monomer composition with an ethylenically unsaturated monomer composition that includes one or more ethylenically unsaturated acceptor monomers, forming a total monomer composition that is substantially free of maleate type monomers and fumarate type monomers; and
(c) polymerizing the mixture resulting from step (b) in the presence of a free radical polymerization initiator. The polymerization is carried out in the substantial absence of Lewis acids and/or transition metals. The monomer of structure (I) is present at a molar excess based on the molar concentration of monomers in the ethylenically unsaturated monomer composition. The ethylenically unsaturated acceptor monomers are present in an amount of at least 15 mol % of the total monomer composition.
Other than in the operating examples, or where otherwise indicated, all numbers or expressions referring to quantities of ingredients, reaction conditions, etc. used in the specification and claims are to be understood as modified in all instances by the term xe2x80x9cabout.xe2x80x9d Various numerical ranges are disclosed in this patent application. Because these ranges are continuous, they include every value between the minimum and maximum values. Unless expressly indicated otherwise, the various numerical ranges specified in this application are approximations.
As used herein the term xe2x80x9ccopolymer compositionxe2x80x9d is meant to include a synthesized copolymer as well as residues from initiators, catalysts and other elements attendant to the synthesis of the copolymer, but not covalently incorporated thereto. Such residues and other elements considered as part of the copolymer composition are typically mixed or co-mingled with the copolymer such they tend to remain with the copolymer when it is transferred between vessels or between solvent or dispersion media.
As used herein, the term xe2x80x9csubstantially freexe2x80x9d is meant to indicate that a material is present as an incidental impurity. In other words, the material is not intentionally added to an indicated composition, but may be present at minor or inconsequential levels because it was carried over as an impurity as part of an intended composition component.
The terms xe2x80x9cdonor monomerxe2x80x9d and xe2x80x9cacceptor monomerxe2x80x9d are used throughout this application. With regard to the present invention, the term xe2x80x9cdonor monomerxe2x80x9d refers to monomers that have a polymerizable ethylenically unsaturated group that has relatively high electron density in the ethylenically double bond, and the term acceptor monomer refers to monomers that have a polymerizable ethylenically unsaturated group that has relatively low electron density in the ethylenic double bond. This concept has been quantified to an extent by the Alfrey-Price Q-e scheme (Greenley, Polymer Handbook, Fourth Edition, Brandrup, Immergut and Gulke, Wiley and Sons, New York, N.Y., pp. 309-319 (1999)). All e values recited herein are those appearing in the Polymer Handbook unless otherwise indicated.
In the Q-e scheme, Q reflects the reactivity of a monomer and e represents the polarity of a monomer, which indicates the electron density of a given monomer""s polymerizable ethylenically unsaturated group. A positive value for e indicates that a monomer has a relatively low electron density and is an acceptor monomer, as is the case for maleic anhydride, which has an e value of 3.69. A low or negative value for e indicates that a monomer has a relatively high electron density and is a donor monomer, as is the case for vinyl ethyl ether, which has an e value of xe2x88x921.80.
As referred to herein, a strong acceptor monomer is meant to include those monomers with an e value greater than 2.0. The term xe2x80x9cmild acceptor monomerxe2x80x9d is meant to include those monomers with an e value greater than 0.5 up to and including those monomers with an e value of 2.0. Conversely, the term strong donor monomer is meant to include those monomers with an e value of less than xe2x88x921.5, and the term xe2x80x9cmild donor monomerxe2x80x9d is meant to include those monomers with an e value of less than 0.5 to those with an e value of xe2x88x921.5.
The present invention is directed to a method of making a copolymer composition containing alternating donor-acceptor segments. The method includes a first step of providing a donor monomer composition that includes an isobutylene type monomer generally described by structure (I): 
where R1 is linear or branched C1 to C4 alkyl and R2 is selected from the group consisting of methyl, linear, cyclic or branched C1 to C20 alkyl, alkenyl, aryl, alkaryl and aralkyl. In a presently preferred embodiment of the invention, the isobutylene type monomers are isobutylene, diisobutylene, dipentene, isoprenol and mixtures thereof.
The group R2 of the donor monomer of structure (I) may include one or more functional groups selected from the group consisting of hydroxy, epoxy, carboxylic acid, ether, carbamate and amide.
In addition to isobutylene type donor monomers, other suitable donor monomers may be included in the present method. Suitable other donor monomers include, but are not limited to, ethylene, butene, styrene, substituted styrenes, methyl styrene, substituted methyl styrenes, vinyl ethers, vinyl esters, vinyl pyridines, divinyl benzene, vinyl naphthalene and divinyl naphthalene. Vinyl esters include vinyl esters of carboxylic acids, which include, but are not limited to, vinyl acetate, vinyl butyrate, vinyl 3,4-dimethoxybenzoate and vinyl benzoate.
Of note in the present method is that the resulting copolymerization method incorporates a substantial portion of alternating residues of a mild donor monomer and a mild acceptor monomer. A non-limiting list of published e values for monomers that may be included as mild donor monomers in the present invention are shown in Table 2.
In a second step of the present method, the donor monomer composition is mixed with an ethylenically unsaturated monomer composition to form a total monomer composition. The ethylenically unsaturated monomer composition includes one or more ethylenically unsaturated acceptor monomers. The ethylenically unsaturated monomer composition is substantially free of maleate type monomers and fumarate type monomers.
The ethylenically unsaturated acceptor monomers comprise one or more monomers described by the structure (II): 
where W is selected from the group consisting of xe2x80x94CN and xe2x80x94X, wherein X is a halide. When W is a xe2x80x94C(xe2x95x90O)OR group, structure (II) represents an acrylic monomer. The present method is particularly directed to copolymers having alternating sequences of monomers of structure (I) and acrylic acceptor monomers.
A non-limiting list of published e values for monomers that may be included as acceptor monomers in the present invention are shown in Table 3.
When the ethylenically unsaturated acceptor monomer is an acrylic acceptor monomer, it is one or more monomers described by structure (III): 
where Y is selected from the group consisting of xe2x80x94NR32, xe2x80x94Oxe2x80x94R5xe2x80x94Oxe2x80x94C(xe2x95x90O)xe2x80x94NR32, and xe2x80x94OR4, R3 is selected from the group consisting of H, linear or branched C1 to C20 alkyl and linear or branched C1 to C20 alkylol, R4 is selected from the group consisting of H, poly(ethylene oxide), poly(propylene oxide), linear or branched C1 to C20 alkyl, alkylol, aryl, alkaryl and aralkyl, linear or branched C1 to C20 fluoroalkyl, fluoroaryl and fluoroaralkyl, a siloxane radical, a polysiloxane radical, an alkyl siloxane radical, an ethoxylated trimethylsilyl siloxane radical and a propoxylated trimethylsilyl siloxane radical, and Rs is a divalent linear or branched C1 to C20 alkyl linking group.
Specific suitable acceptor monomers include, but are not limited to, hydroxyethyl acrylate, hydroxypropyl acrylate, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, isobornyl acrylate, dimethylaminoethyl acrylate, acrylamide, perfluoro methyl ethyl acrylate, perfluoro ethyl ethyl acrylate, perfluoro butyl ethyl acrylate, trifluoromethyl benzyl acrylate, perfluoro alkyl ethyl, acryloxyalkyl terminated polydimethylsiloxane, acryloxyalkyl tris(trimethylsiloxy silane), acryloxyalkyl trimethylsiloxy terminated polyethylene oxide, chlorotrifluoro ethylene, glycidyl acrylate, 2-ethylhexyl acrylate and n-butoxy methyl acrylamide.
In an embodiment of the present method, the group represented by Y includes at least one suitable functional group. Suitable functional groups for Y include, but are not limited to, epoxy, carboxylic acid, hydroxy, amide, ether, ester, isocyanate, amine, thioether and sulfide.
In an embodiment of the present method, the monomer of structure (I) is present in the total monomer composition at a molar excess based on the amount of acrylic acceptor monomer. Any amount of excess monomer of structure (I) may be used in the present invention in order to encourage the formation of the desired alternating copolymer architecture. The excess amount of monomer of structure (I) may be at least 10 mol %, in some cases up to 25 mol %, typically up to 50 mol % and in some cases up to 100 mol % based on the amount of acrylic acceptor monomer. When the molar excess of monomer of structure (I) is too high, the method may not be economical on a commercial scale.
In a further embodiment of the present method, the acrylic acceptor monomer of structure (III) is present in an amount of at least 15 mol %, in some cases 17.5 mol %, typically at least 20 mol % and in some cases 25 mol % of the total monomer composition. The acrylic acceptor monomer may further be present in an amount up to 50 mol %, in some cases up to 47.5 mol %, typically up to 45 mol % and in some cases up to 40 mol % of the total monomer composition. The level of the acrylic acceptor monomers used is determined by the properties that are to be incorporated into the copolymer composition. The acrylic acceptor monomers may be present in the monomer composition in any range of values inclusive of those stated above.
The use of other acceptor monomers is optional in the present method. Suitable other acceptor monomers that may be used in the present invention include, but are not limited to, acrylonitrile, methacrylonitrile, vinyl halides, crotonic acid, vinyl alkyl sulfonates and acrolein. When other mild acceptor monomers are present, they are present at a level of at least 0.01 mol % of the total monomer composition, often at least 0.1 mol %, typically at least 1 mol % and in some cases at least 2 mol % of the total monomer composition. The other acceptor monomers may be present at up to 35 mol %, in some cases up to 25 mol %, typically up to 15 mol % and in some cases up to 10 mol % of the total monomer composition. The level of other acceptor monomers used herein is determined by the properties that are to be incorporated into the copolymer. The other acceptor monomers may be present in any range of values inclusive of those stated above.
The ethylenically unsaturated monomer composition of the present method may include other ethylenically unsaturated monomers. The other monomers may include ethylenically unsaturated monomers of general structure (V): 
wherein R11, R12 and R14 are independently selected from the group consisting of H, CF3, straight or branched alkyl of 1 to 20 carbon atoms, aryl, unsaturated straight or branched alkenyl or alkynyl of 2 to 10 carbon atoms, unsaturated straight or branched alkenyl of 2 to 6 carbon atoms substituted with a halogen, C3-C8 cycloalkyl, heterocyclyl and phenyl; R13 is selected from the group consisting of H, C1-C6 alkyl, COOR15 wherein R15 is selected from the group consisting of H, an alkali metal, a C1 to C6 alkyl group, glycidyl and aryl.
As used herein and in the claims, xe2x80x9cother ethylenically unsaturated radically polymerizable monomerxe2x80x9d and like terms are meant to include vinyl monomers, allylic monomers, methacrylic monomers, olefins and other ethylenically unsaturated monomers that are radically polymerizable and not classified as donor monomers or acceptor monomers.
Examples of classes of vinyl monomers from which the other ethylenically unsaturated radically polymerizable monomers may be selected include, but are not limited to, methacrylic monomers and allylic monomers. When the other ethylenically unsaturated radically polymerizable monomers are methacrylic monomers, they may be at least one of alkyl methacrylate having from 1 to 20 carbon atoms in the alkyl group. Specific examples of alkyl methacrylates having from 1 to 20 carbon atoms in the alkyl group include, but are not limited to, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, 3,3,5-trimethylcyclohexyl methacrylate as well as functional methacrylates, such as hydroxyalkyl methacrylates, epoxy functional methacrylates and carboxylic acid functional methacrylates.
The other ethylenically unsaturated radically polymerizable monomers may also be selected from monomers having more than one methacrylate groups, for example, methacrylic anhydride and diethyleneglycol bis(methacrylate).
As used herein and in the claims, by xe2x80x9callylic monomer(s)xe2x80x9d what is meant is monomers containing substituted and/or unsubstituted allylic functionality, i.e., one or more radicals represented by the following general structure (V),
H2Cxe2x95x90C(R10)xe2x80x94CH2xe2x80x94xe2x80x83xe2x80x83(V) 
where R10 is hydrogen, halogen or a C1 to C4 alkyl group. Most commonly, R10 is hydrogen or methyl and consequently general structure (VIII) represents the unsubstituted (meth)allyl radical, which encompasses both allyl and methallyl radicals. Examples of allylic monomers include, but are not limited to, (meth)allyl alcohol; (meth)allyl ethers, such as methyl (meth)allyl ether; allyl esters of carboxylic acids, such as (meth)allyl acetate, (meth)allyl butyrate, (meth)allyl 3,4-dimethoxybenzoate and (meth)allyl benzoate.**
When other ethylenically unsaturated monomers are present, they are present at a level of at least 0.01 mol % of the total monomer composition, often at least 0.1 mol %, typically at least 1 mol % and in some cases at least 2 mol % of the total monomer composition. The other monomers may be present at up to 35 mol %, in some cases up to 25 mol %, typically up to 15 mol % and in some cases up to 10 mol % of the total monomer composition. The level of other monomers used herein is determined by the properties that are to be incorporated into the copolymer. The other ethylenically unsaturated monomers may be present in the total monomer composition in any range of values inclusive of those stated above.
The mixture of the total monomer composition is polymerized in the presence of a free radical polymerization initiator in the substantial absence of Lewis acids and transition metals. Any suitable free radical polymerization initiator may be used in the present invention. Suitable free radical initiators are typically thermal free radical initiators. Suitable thermal free radical initiators include, but are not limited to, peroxide compounds, azo compounds and persulfate compounds.
Examples of suitable thermal free radical initiator peroxide compounds include, but are not limited to, hydrogen peroxide, methyl ethyl ketone peroxides, benzoyl peroxides, di-t-butyl peroxides, di-t-amyl peroxides, dicumyl peroxides, diacyl peroxides, decanoyl peroxide, lauroyl peroxide, peroxydicarbonates, peroxyesters, dialkyl peroxides, hydroperoxides, peroxyketals and mixtures thereof.
Examples of suitable thermal free radical initiator azo compounds include, but are not limited to, 4-4xe2x80x2-azobis(4-cyanovaleric acid), 1-1xe2x80x2-azobiscyclohexanecarbonitrile), 2-2xe2x80x2-azobisisobutyronitrile, 2-2xe2x80x2-azobis(2-methylpropionamidine) dihydrochloride, 2-2xe2x80x2-azobis(2-methylbutyronitrile), 2-2xe2x80x2-azobis(propionitrile), 2-2xe2x80x2-azobis(2,4-dimethylvaleronitrile), 2-2xe2x80x2-azobis(valeronitrile), 2,2xe2x80x2-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 4,4xe2x80x2-azobis(4-cyanopentanoic acid), 2,2xe2x80x2-azobis(N,Nxe2x80x2-dimethyleneisobutyramidine), 2,21-azobis(2-amidinopropane) dihydrochloride, 2,2xe2x80x2-azobis(N,Nxe2x80x2-dimethyleneisobutyramidine) dihydrochloride, 2-(carbamoylazo)-isobutyronitrile and mixtures thereof.
In an embodiment of the present invention, the ethylenically unsaturated monomer composition and the free radical polymerization initiator are separately and simultaneously added to and mixed with the donor monomer composition. The ethylenically unsaturated monomer composition and the free radical polymerization initiator may be added to the donor monomer composition over a period of at least 15 minutes, in some cases at least 20 minutes, typically at least 30 minutes and in some cases at least 1 hour. The ethylenically unsaturated monomer composition and the free radical polymerization initiator may further be added to the donor monomer composition over a period of up to 24 hours, in some cases up to 18 hours, typically up to 12 hours and in some cases up to 8 hours. The time for adding the ethylenically unsaturated monomer must be sufficient to maintain a suitable excess of donor monomer of structure (I) over unreacted acrylic acceptor monomer to encourage the formation of donor monomerxe2x80x94acceptor monomer alternating segments. The addition time is not so long as to render the process economically unfeasible on a commercial scale. The addition time may vary in any range of values inclusive of those stated above.
After mixing or during addition and mixing, polymerization of the monomers takes place at a suitable temperature. The present polymerization method can be run at any suitable temperature. Suitable temperatures for the present method may be ambient, at least 50xc2x0 C., in many cases at least 60xc2x0 C., typically at least 75xc2x0 C. and in some cases at least 100xc2x0 C. Suitable temperatures for the present method may further be described as being up to 300xc2x0 C., in many cases up to 275xc2x0 C., typically up to 250xc2x0 C. and in some cases up to 225xc2x0 C. The temperature is typically high enough to encourage good reactivity from the monomers and initiators employed. However, the volatility of the monomers and corresponding partial pressures create a practical upper limit on temperature determined by the pressure rating of a reaction vessel employed. The polymerization temperature may vary in any range of values inclusive of those stated above.
The present polymerization method can be run at any suitable pressure. A suitable pressure for the present method may be ambient, at least 1 psi, in many cases at least 5 psi, typically at least 15 psi and in some cases at least 20 psi. Suitable pressures for the present method may further be described as being up to 200 psi, in many cases up to 175 psi, typically up to 150 psi and in some cases up to 125 psi. The pressure is typically high enough to maintain the monomers and initiators in a liquid phase. The pressures employed have a practical upper limit based on the pressure rating of the reaction vessel employed. The pressure during polymerization may vary in any range of values inclusive of those stated above.
When the polymerization is completed, a portion of the monomer of structure (I) will typically remain because it did not polymerize. The unreacted portion of the monomer of structure (I) is substantially removed from the resulting copolymer composition by evaporation. In an embodiment of the present invention, the removal of the unreacted portion of the monomer of structure (I) is facilitated by the application of a vacuum.
In an embodiment of the present method of making a copolymer composition containing alternating donor-acceptor segments, the method includes the steps of (a) providing a donor monomer composition that includes one or a combination of isobutylene, diisobutylene, dipentene and isoprenol; (b) mixing the donor monomer composition with an ethylenically unsaturated monomer composition to make a total monomer composition that is substantially free of maleate or fumarate type monomers and includes one or more acrylic acceptor monomers of structure (III) and (c) polymerizing the total monomer composition in the presence of a free radical polymerization initiator in the substantial absence of Lewis acids and transition metals.
The donor monomer composition is present at a molar excess of at least 10 mol % based on the molar concentration of acrylic acceptor monomer, and the acrylic acceptor monomer is present in an amount of at least 15 mol % of the total mols of the total monomer composition.
The method of the present invention provides a copolymer composition that includes a copolymer. The copolymer contains at least 30 mol %, in many cases at least 40 mol %, typically at least 50 mol %, in some cases at least 60 mol % and in other cases at least 75 mol % of monomer residues derived from alternating sequences of donor monomerxe2x80x94acceptor monomer pairs. The alternating monomer residue pairs can be described as:
-[DM-AM]-
where DM represents a residue from a donor monomer and AM represents a residue from an acceptor monomer. The copolymer may be a 100% alternating copolymer of DM and AM. More particularly, at least 15 mol % of the copolymer includes a donor monomer of structure (I) and is substantially free of maleate and/or fumarate monomer residues. When maleate and/or fumarate monomer residues are present, they can result in multifunctional monomers with too many functional groups in the copolymer. This can create problems, for example, in coatings where a thermosetting composition may have a short shelf life due to the overly functional nature of the copolymer.
Further, a copolymer composition that results from the present method is substantially free of transition metals and Lewis acids, which as noted above, have been used in the prior art to make alternating copolymers of mild donor monomers and mild acceptor monomers. The present invention does not utilize transition metals or Lewis acid adjuncts in preparing the present copolymer composition; therefore, they need not be removed after polymerization, and the resulting copolymer compositions will not suffer the drawbacks inherent in those that contain transition metals or Lewis acids.
The copolymer that results from the present method has a molecular weight of at least 250, in many cases at least 500, typically at least 1,000 and in some cases at least 2,000. The present copolymer may have a molecular weight of up to 1,000,000, in many cases up to 500,000, typically up to 100,000 and in some cases up to 50,000. Certain applications will require that the molecular weight of the present copolymer not exceed 25,000, in some cases not exceed 20,000 and in certain instances not exceed 16,000. The molecular weight of the copolymer is selected based on the properties that are to be incorporated into the copolymer composition. The molecular weight of the copolymer may vary in any range of values inclusive of those stated above.
The polydispersity index (PDI) of the copolymer produced using the present method is not always critical. The polydispersity index of the copolymer is usually less than 4, in many cases less than 3.5, typically less than 3.0 and in some cases less than 2.5. As used herein, and in the claims, xe2x80x9cpolydispersity indexxe2x80x9d is determined from the following equation: (weight average molecular weight (Mw)/number average molecular weight (Mn)). A monodosperse polymer has a PDI of 1.0. Further, as used herein, Mn and Mw are determined from gel permeation chromatography using polystyrene standards.
In an embodiment of the present invention, the copolymer produced by the present method may include alternating sequences of donor monomerxe2x80x94acceptor monomer residue pairs that have the alternating structure (VI): 
where R1, R2 and W are defined as above. A particularly preferred embodiment is one wherein the monomer residues containing the group W are derived from one or more acrylic monomers, and the monomer residues containing the groups R1 and R2 are derived from one or a combination of diisobutylene, isobutylene, dipentene and isoprenol. The copolymer compositions of the present invention may also include other polymerizable ethylenically unsaturated monomers.
The copolymer composition resulting from the present method may have all of the incorporated monomer residues in an alternating architecture. A non-limiting example of a copolymer segment having 100% alternating architecture of diisobutylene (DIIB) and an acrylic monomer (Ac) is shown by structure (VII):
-Ac-DIIB-Ac-DIIB-Ac-DIIB-Ac-DIIB-Ac-DIIB-Ac-DIIB-Ac-xe2x80x83xe2x80x83(VII) 
However, in most instances, the copolymer resulting from the present method will contain alternating segments and random segments as shown by structure (VIII), a copolymer of DIIB, Ac and other monomers, M: 
Structure (VIII) shows an embodiment of the present invention where the copolymer may include alternating segments, as shown in the boxes, and random segments, as shown by the underlined segments.
The random segments of the copolymer may contain donor or acceptor monomer residues that have not been incorporated into the copolymer composition by way of an alternating architecture. The random segments of the copolymer composition may further include residues from other ethylenically unsaturated monomers. As recited herein, all references to polymer segments derived from alternating sequences of donor monomerxe2x80x94acceptor monomer pairs are meant to include segments of monomer residues such as those shown by the boxes in structure (VIII).
The copolymer that results from the present method may be utilized as a starting material for the preparation of other polymers by using functional group transformations by methods known in the art. Functional groups that can be introduced by these methods are epoxy, carboxylic acid, hydroxy, amide, oxazoline, acetoacetate, isocyanate, carbamate, amine, amine salt, quaternary ammonium, thioether, sulfide, sulfonium and phosphate.
For example, a copolymer of the present method comprising methyl acrylate will contain carbomethoxy groups. The carbomethoxy groups can be hydrolyzed to carboxyl groups or transesterified with an alcohol to form the corresponding ester of the alcohol. Using ammonia, the aforementioned methyl acrylate copolymer can be converted to an amide, or, using a primary or secondary amine, can be converted to the corresponding N-substituted amide. Similarly, using a diamine such as ethylene diamine, one can convert the aforementioned copolymer of the present method to an N-aminoethylamide, or, with ethanolamine, to an N-hydroxyethylamide. The N-aminoethylamide functionality can be further converted to an oxazoline by dehydration. The N-aminoethylamide can be further reacted with a carbonate such as propylene carbonate to produce the corresponding urethane functional copolymer. These transformations can be carried out to convert all of the carbomethoxy groups or can be carried out in part, leaving some of the carbomethoxy groups intact.
Epoxy groups can be introduced into the copolymer of the present method directly by using glycidyl acrylate in the copolymer preparation or indirectly by functional group transformation. One example of an indirect method is to oxidize residual unsaturation in the copolymer to epoxy groups using a peracid such as peroxyacetic acid. Alternatively one can prepare a carboxyl-functional copolymer by hydrolysis as described above, treat the carboxyl-functional copolymer with epichlorohydrin then alkali to produce the epoxy functional copolymer. These transformations can also be carried out exhaustively or in part. The resulting epoxy-functional copolymer can be further reacted with the appropriate active hydrogen containing reagents to form alcohols, amines or sulfides.
Hydroxyl groups can be introduced directly using a hydroxyl-functional monomer such as hydroxyethyl acrylate in the copolymer of the present method, or they can be introduced by functional group transformation. By treating the carboxyl-functional copolymer described above with an epoxy one can produce a hydroxyl functional polymer. Suitable epoxies include, but are not limited to, ethylene oxide, propylene oxide, butylene oxide and glycidyl neodecanoate.
The above-described hydroxyl functional copolymers can be further reacted to form other copolymers. For example, a copolymer containing hydroxyethyl groups can be treated with a carbamylating agent, such as methyl carbamate, to produce the corresponding carbamate functional copolymer. With diketene or t-butyl acetoacetate the hydroxyl groups can also be converted to acetoacetate esters.
Isocyanate functional copolymers can also be produced. Copolymers of the present method, which contain 2 or more hydroxyl groups, can be treated with a diisocyanate such as isophoronediisocyanate to produce isocyanate-functional polymers. Primary amine functional copolymers, described above, can be phosgenated to produce isocyanate functionality.
Ionic functionality can be incorporated into the copolymer of the present method by any means known in the art. Carboxylate groups can be introduced by hydrolysis of ester groups in the copolymer followed by reaction with base. Amine salts can be introduced by preparing the present copolymer with an amine functional acrylate, such as dimethylaminoethyl acrylate, followed by protonation of the amino groups with an acid. Amine salts can also be introduced by reacting a glycidyl functional copolymer with ammonia or an active hydrogen containing amine followed by protonation with acid. Quaternary amine functional groups or ternary sulfonium groups can be introduced into the copolymer by treating an epoxy functional copolymer of the present method with a tertiary amine or sulfide, respectively, in the presence of a protic acid.
The present invention is more particularly described in the following examples, which are intended to be illustrative only, since numerous modifications and variations therein will be apparent to those skilled in the art. Unless otherwise specified, all parts and percentages are by weight.